El Niño brings drought to the southern hemisphere, and floods to its northern counterpart. Its last arrival, across 2015 and 2016, created two years of drought throughout Southern Africa.
Millions of people went hungry as crops failed - yields from South Africa’s critical maize crop halved from 14 to seven-million tonnes. But in east Africa, the phenomena brought heavy rains and flooding.

New research now says this also adds 50 000 cases of cholera across that region, for each year that the regular phenomenon is around. This is according to a team from Johns Hopkins Bloomberg School of Public Health, publishing their findings in the Proceedings of the National Academy of Sciences. It also decreased the number of cases in Southern Africa by 30 000 a year; with a drought, people are less likely to drink infected water from now dried-up rivers. Sewage plants also take less strain so are less likely to release E. coli-laden water into what water there is in rivers.

A sudden increase of 50 000 cases is a big jump for countries struggling to contain the disease. At the same time, a drop of 30 000 cases, is also a significant change. World Health Organisation numbers estimate that there are up to four-million cholera cases around the world each year, with between 21 000 and 143 000 deaths a year. Some 40% of all these cases are in Africa.

The team looked at satellite data from El Niño years between 2000 and 2014, mapping cholera cases before, during and after each occurrence of the phenomenon. By rapidly warming the Pacific Ocean, this changes global weather far quicker than any other single force. Climate change projections show that its intensity and regularity have already started increasing in a rapidly warming world.

This is a problem for countries that already have little breathing space when it comes to weather-related disasters. When it does rain, sewerage systems are overwhelmed and that sewage then flows into rivers and drinking water systems. That results in diseases such as cholera. This leads to severe vomiting, diarrhea and, if left untreated, up to 30% of patients die.

When it isn’t raining, those polluted water systems and rivers still carry diseases - which people then contract because they rely on rivers for drinking and cooking water.

The Johns Hopkins research - “El Niño and the shifting geography of cholera in Africa” - said their findings should help stop these kinds of spikes in the future. Because of its global impact, there is a lot of data gathering in the Pacific where El Niño starts its warming. That means countries generally have a six month to one year warning that it is coming.

Governments can then get treatment facilities and medicine in place in areas where they can expect cholera. The research said: “If you have cholera centres available, fast, supportive care can reduce the fatality rate from cholera from as high as 30-percent to nothing.”

Sipho Kings

Sipho Kings is the Mail & Guardian's environment reporter. Broken ecosystems, bad corporations and mean people are the order of the day. This means his shoes are caked in all sorts of dodgy material. Read more from Sipho Kings